The United States is the leading beef producer of the world. In 2003, the United States produced over 26 billion pounds of beef and the United States per capita consumption averaged 64 pounds. Beef averages approximately 31 percent of the total per capita consumption of meat; however, beef's share of consumer retail spending was 40.2 percent of the total dollars spent on meat in 2000. Thus, the United States beef industry is a very diverse multi-billion dollar enterprise.
The United States feedlot industry traditionally functions to grow and finish weaned calves (˜400–600 pounds) and yearling steers and heifers (550 to 800 pounds) to slaughter weights of approximately 1,100 to 1400 pounds. Because the feedlot industry increases the size and quality of cattle, the industry is constantly driven to increase the rate and efficiency of gain of cattle. The use of growth enhancing agents by the feedlot industry can be easily visualized in that beef (meat) production has risen dramatically over the last several years, while the number of cattle has been in recent decline.
Feedlots are confinement feeding operations where cattle are fed primarily high energy finishing diets prior to harvest. Most feedlot operations feed a relatively high grain diet for 90 to 225 days (depending on starting body weight) resulting in economically efficient weight gains and improved palatability of the retail product. The very nature of a feedlot is to put as much weight on an animal in the least amount of time as possible. This process results in a number of nutritional diseases such as lactic acidosis, feedlot bloat, liver abscesses, polioencephalomalacia, and others. Of these diseases acidosis is the most important and costly nutritional disorder in United States feedlots today.
Lactic Acidosis
Acidosis is caused by a rapid production and absorption of acids, mostly lactic acid, from the rumen when cattle consume too much starch (grain) or sugar in short amount of time. As long as cattle are finished on high energy (grain) diets, lactic acidosis will remain a serious problem in the feedlot industry. Acidosis is not one disorder, rather a continuum of degrees of acidosis. The effects of this continuum of acidosis can be slight, reducing feed intake by ˜0.25 lbs/day, or severe enough to result in death. Several acidosis-related problems occur in the feedlot including, sudden death syndrome, polioencephalomalacia, founder, rumenitis, liver abscesses, malabsorption, clorstridial infestations, off-feed, and reduced feed intake.
Typical feedlot acidosis occurs when a large amount of highly fermentable feed (grain) is consumed in a short amount of time resulting in the production of more lactic acid than can be buffered by the rumen. This results in water from the circulatory system being drawn into the rumen, resulting in the rest of the body being dehydrated and pronounced changes in blood pH. Signs can be sub-acute to acute.
Liver abscesses result from a disease complex known as the acidosis-rumenitis-liver abscess complex. Fusobacterium necrophorum, a normal inhabitant of the rumen, is the primary causative bacteria. Feeding a high energy grain diet causes ruminal acidosis, as explained above, which attacks the integrity of the rumen wall, permitting opportunistic bacteria such as Fusobacterium necrophorum to colonize, enter the bloodstream, and eventually enter and infect the liver. High-concentrate diets also impact the severity and incidence of liver abscesses and acidosis. As the energy levels of the grain rations increase, problems associated with acidosis increase. This cause and effect relationship creates an interesting paradigm, considering the very nature of the feedlot is to put on rapid weight.